A cell-permeable isoquinolinedione compound that potently inhibits PARP-1 activity in a NAD+-competitive and reversible manner. Affects PPAR-2 activity with lower potency. Selectively inhibits PARP-1-mediated cellular PAR formation and is of little effect against PAR formation in fibroblasts derived from parp-1(-/-) mice. Its in vivo application is limited